Garden Orb spiders (Eriophora transmarina) are very common garden spiders, especially around large trees at night when they come out to build their webs. Their scare-factor is high as the webs can span large distances across paths or between trees, easily walked into in twilight or the dark. The spider itself is not aggressive and not normally seen during the day.
They are fairly large, with a body about the size of an adults thumbnail, and long legs. The local species tend to have a strong reddish colouration to their legs when extended.
The spiders can be seen in their webs at dawn and dusk, and occasionally during the day if the weather is overcast. Sometimes if the web has survived the night intact they will secrete themselves away in a sheltered spot, running out to quickly subdue any hapless insect that flies or crawls into it, before scurrying back to safety.
The image above is of the same spider – front and back. She had spun her web in a normally shaded spot that receives brief winter sunlight in the late afternoon. The left hand image with the sun acting as a back-light indicates how translucent those long, solid looking legs and thorax really are.
More information on this and other Australian Spiders can be found at http://www.findaspider.org.au/find/spiders/105.htm